Study alterations in the serological reactivity pattern in mice at high risk to developing carcinogen-induced or endogeneous virus-induced malignancies as well as on reactivity of such mice towards antigens associated with the relevant tumors. Model systems are to be: spontaneous tumors in C3Hf mice; mammary tumors induced by DMBA in BALB/c mice; and lung adenomas appearing in urethane-treated BALB/c mice.